It is common practice by those of ordinary skill in the art to shield high frequency circuits to prevent the high frequency (typically RF) energy from radiating (spraying) into other circuits and degrading their performance. Often, circuits such as power amplifiers or voltage controlled oscillators (VCO's) are placed in metal cast housings having a metal cover (generally steel) to enclose the circuit. Any radiated energy is conducted to ground by the metal housing and cover, thereby shielding the exterior circuits from the contaminating energy.
However, such shielding practices may impair the performance of the high frequency circuit in adverse conditions such as vibration and temperature. Those skilled in the art will appreciate that high frequency circuits are affected by stray capacitance created by the metal cover and metal plating on the printed circuit (PC) board or substrate upon which the high frequency circuit is mounted. The stray capacitance is a function of the distance between the cover and the substrate. In vibration, the metal cover generally vibrates at one rate while the substrate vibrates at another rate. This creates a time varying capacitance due to the changing distances between the cover and the substrate. Thus, the benefit obtained by the generally accepted engineering practice of shielding the high frequency circuit incorporates the detriment of poor vibration performance. Accordingly, there is a need in the art for a method and apparatus for minimizing the vibration degradation experienced by shielded circuits.